DE-A-1,265,109 teaches a sewing thread of twisted, endless, synthetic threads onto which a dried dispersion is applied in an expensive work process. However, the purpose of the preparation thereby is not the concentration of the thread circumference but that a sufficient thread-on-thread adhesion should be achieved in order to prevent a shifting of the thread and an undesired falling off of the outer thread layers on the sewing-yarn or thread body.
The dispersion mentioned in DE-A-1,265,106 can not be washed out in the actual sense but rather must be dissolved with organic solvents. However, the use of such organic solvents contravenes the legal regulations for the treatment of textiles for human use. The organic solvents cited in this prior publication can therefore not be used for articles of clothing.
Many requirements are placed on a sewing yarn or thread, especially, it should be able to be processed on machines, even on automatic sewing machines, and meet special conditions regarding quality and softness of a seam sewn therewith.
Traditional sewing yarns have the problem that they require a construction, on account of the demands placed on them, which has a certain hardness after the sewing and in the seam.
A quite essential quality feature of a seam is that the two areal structures to be connected are joined via the seam in such a manner that the desired softness is achieved and a gapping of the seam as well as fraying are avoided. Only in this manner can the functional and esthetic requirements of a seam be met.
The cause for the seam wrinkling is to be found in the fact that the sewing thread is too strongly elongated or stretched when passing through the guides and the thread levers of the sewing machine. After the sewing process the sewing thread shortens back into its initial length (memory effect). As a result thereof, the undesired seam wrinkling occurs in the seam since the thread can only go back by the contraction of the flexible areal structures in the seam. The back formation takes place successively as a function of the stability of the flexible areal structure, that is, of the materials to be sewn. The back formation of the thread can take place, depending on structure and composition, wherein one hour but possibly also not until after a few days. In certain instances the back formation takes place only after one or several washing processes or cleaning processes. This depends in the particular individual instance on within which times and by means of which processes the stabilizing agents contained in the fabric can be dissolved or converted by the washing or the cleaning.
It can basically be stated that the seam wrinkling always occurs if the back formation force of the sewing thread is greater than the stability of the material connected by the sewing thread via the seam.
The invention has the problem of creating a sewing thread which is designed so that the desired seam strength is achieved by the elongation during sewing but the restoration forces (memory effect) which otherwise take effect within a time period can not occur.
A further essential quality feature of a seam is that it does not affect the wearing properties and is not perceived as being very troubling. The fact is disadvantageous in particular in the case of bathing garments, underwear, bodices and the like that the softness of these garments worn directly on the body is lost when traditional sewing yarns are used.
The invention has the problem of preparing a bulk yarn or thread which ordinarily can not be sewn as a needle thread or can not be economically sewn and to process it in such a manner that it can be sewn on modern sewing machines and automatic machines and that the seam strength given by the raw material and the construction of the sewing yarn achieves the original softness again even after the sewing and after a subsequent washing.
The problem of the invention is solved by the features of claim 1.
Advantageous further developments result from the subclaims.